1. Field of the Invention
The present invention relates to a numerical control apparatus incorporating therein a programmable controller.
2. Description of Related Art
A numerical control apparatus for controlling a machine tool or the like incorporates a programmable controller that performs sequence control or other control of the machine controlled by the numerical control apparatus. Generally, a sequence program executed by the programmable controller is displayed in the form of a ladder diagram or the like on a screen of a display unit of the numerical control apparatus. In displaying, sometimes displayed are: a ladder diagram representative of the sequence program; addresses of signals; symbols representative of names or identifiers given to these signals; and comments for ease of maintenance service, etc. Also adopted is a method in which a required message giving instructions to an operator is displayed on the display screen during the execution of the sequence program. In this method, it is known to enable the operator to select a language in which the message is displayed, so that the message may be displayed in the selected language. For example, in the known art, the message is displayed in Japanese when the operator selects the Japanese language, and displayed in English when the English language is selected (see JP 5-80815A).
The symbols mentioned above are names or identifiers that are given to signals appearing in the sequence program and that indicate the properties or meanings of these signals, thus aiding the understanding of the sequence program. Generally, the symbols are displayed in English.
The comments referred to by the operator when he/she performs the maintenance of the sequence program are constituted by pieces of character information serving as additional information for easier understanding and/or maintenance operation of signals appearing in the sequence program or of part or the entire of the sequence program.
The symbols and the comments are stored as part of the sequence program in the programmable controller. That is to say, the sequence program is constituted by objects in the body of program, the symbols and the comments for signals, and other data.
In the thus constructed sequence program, pieces of information given by the symbols and the comments are ancillary ones for ease of understanding and maintenance of the sequence program, and do not affect directly on sequence program operations. In manufacturing a machine having a programmable controller, therefore, some manufacturers sometimes intentionally omit symbols and/or comments in order to reduce the volume of the sequence program or to intentionally make it difficult to analyze the sequence program. Meanwhile, messages are different in purpose or purport from comments in that they are intended, as mentioned above, to give some instructions to the operator and not directly relate to signals or the like.
Conventionally, the symbol or the comment can only define single character information for a corresponding signal or the like. Even if pieces of character information are defined for each signal, their intended use is fixed and the way of use is limited. As for the symbol, which is a name or an identifier of a signal, even when it is displayed in single character information (language), no substantial problem is caused. On the other hand, if the comment serving as information for explaining the content of a signal or of the sequence program is displayed in single character information (in English, for example), the advantage thereof is reduced especially in multinational use. In order to adapt the comment to a plurality of languages, there occurs a problem that a plurality of sequence programs must be prepared that are written in various languages (Japanese, English, French, German, etc.).